1. Field of Invention
The present invention is relating to a fabricating method of field emission triodes. In particularly, the present invention is relating to a fabricating method of field emission triodes having carbon nanotubes.
2. Description of Related Art
Field emission displays (FED) have became more and more valued because of having superior brightness, wide viewing angle, transient response swiftness, and other advantages. In addition, carbon nanotubes have a property of lower initiating electric field so that the carbon nanotubes are the preferred cathode emitter material for the field emission display.
In the conventional manufacturing technology of carbon nanotube field emission device, chemical vapor deposition is usually used to directly grow the carbon nanotubes at the cathode region coated by a metal catalyst. However, the carbon nanotubes formed using this method exhibit nonuniform distribution. Under the typical field emission operating conditions, the number of carbon nanotubes in the same parallel orientation direction is relatively low, and thus the threshold voltage and emission current density are not meet the requirements. Furthermore, the tube density distribution of the carbon nanotubes is not easy to control if the carbon nanotubes are grown using this method. It leads to uneven current density distribution and phosphor emitting brightness. Furthermore, under high electric field operation, adhesion between the carbon nanotubes and the substrate is yet to be tested.
Taiwan Patent 428189 discloses a fabrication method for a cathode array using carbon nanotubes. However, in the prior art, the formed aluminum anodization film has poor pore diameter uniformity, distributive uniformity, and vertical alignment. As a result, the pipe diameter uniformity, distributive uniformity, and vertical alignment of the carbon nanotubes formed inside the pores are deteriorated, and thus the field emission characteristic of the carbon nanotubes is also poor. Furthermore, Taiwan Patent 428189 uses aluminum or aluminum alloy as cathode lines. However, aluminum has a lower melting point, and thus the subsequent processing temperature should be lower than 450° C. Hence, only lower temperature chemical vapor deposition can be used to grow carbon nanotubes. Furthermore, using aluminum or aluminum alloy as cathode lines has disadvantages of that when the carbon nanotube field emission device is operated under high current conditions, electromigration may be easily produces at the cathode lines which leads to open circuit.